Metrics2: Store a registry of Counters

go/metrics2/counter.go

 package metrics2
 
-import "sync"
+import (
+        "fmt"
+        "sync"
+
+        "github.com/skia-dev/glog"
+        "go.skia.org/infra/go/util"
+)
 
 const (
         MEASUREMENT_COUNTER = "counter"
 )
 
 // Counter is a struct used for tracking metrics which increment or decrement.
 type Counter struct {
         m   *Int64Metric
         mtx sync.Mutex
 }
 
-// NewCounter creates and returns a new Counter.
-func (c *Client) NewCounter(name string, tags map[string]string) *Counter {
-        // Add the name to the tags.
-        t := make(map[string]string, len(tags)+1)
-        for k, v := range tags {
-                t[k] = v
+// GetCounter creates or retrieves a Counter with the given name and tag set and
+// returns it.
+func (c *Client) GetCounter(name string, tagsList ...map[string]string) *Counter {
+        c.countersMtx.Lock()
+        defer c.countersMtx.Unlock()
+
+        // Make a copy of the concatenation of all provided tags.
+        tags := util.AddParams(map[string]string{}, tagsList...)
+        tags["name"] = name
+        md5, err := util.MD5Params(tags)
+        if err != nil {
+                glog.Errorf("Failed to encode measurement tags: %s", err)
         }
-        t["name"] = name
-        return &Counter{
-                m:   c.GetInt64Metric(MEASUREMENT_COUNTER, t),
-                mtx: sync.Mutex{},
+        key := fmt.Sprintf("%s_%s", MEASUREMENT_COUNTER, md5)
+        m, ok := c.counters[key]
+        if !ok {
+                m = &Counter{
+                        m: c.GetInt64Metric(MEASUREMENT_COUNTER, tags),
+                }
+                c.counters[key] = m
         }
+        return m
 }
 
-// NewCounter creates and returns a new Counter using the default client.
-func NewCounter(name string, tags map[string]string) *Counter {
-        return DefaultClient.NewCounter(name, tags)
+// GetCounter creates and returns a new Counter using the default client.
+func GetCounter(name string, tags map[string]string) *Counter {
+        return DefaultClient.GetCounter(name, tags)
 }
 
 // Inc increments the counter by the given quantity.
 func (c *Counter) Inc(i int64) {
         c.mtx.Lock()
         defer c.mtx.Unlock()
         c.m.Update(c.m.Get() + i)
 }
 
 // Dec decrements the counter by the given quantity.
 func (c *Counter) Dec(i int64) {
         c.mtx.Lock()
         defer c.mtx.Unlock()
         c.m.Update(c.m.Get() - i)
 }
 
 // Reset sets the counter to zero.
 func (c *Counter) Reset() {
         c.mtx.Lock()
         defer c.mtx.Unlock()
         c.m.Update(0)
 }
 
 // Get returns the current value in the counter.
 func (c *Counter) Get() int64 {
         c.mtx.Lock()
         defer c.mtx.Unlock()
         return c.m.Get()
 }